DH-106 Comet

The Comet 2 was an upgrade from DH-Ghost engines to Rolls-Royce Avon engines. Avons were axial-flow engines. The immediate benefit was 46% increase in thrust, greater payload, an increase from 36 to 44 passengers, and longer range.

The Avon engine had been eagerly awaited by de Havilland. Axial engines were fundamentally more efficient than centrifugal designs, but, in fact, the idea was older: the first patent for a gas-turbine was an axial-flow type by Dr. A. A. Griffith in 1926; but contemporary knowledge and materials had not been up to the task. Whittle's centrifugal design had been realistically achievable, and became the preferred choice for the first generation of British jet engines. Despite enormous war-time investment by Germany in axial-flow engines, this type of engine did not match the reliability of centrifugal engines until 1949.

For the Comet, the Rolls-Royce Avon reduced operating costs per ton, and opened new routes. The largest orders were from BOAC (12) and Air France (6). At end of 1953, the total number of Comet 2 orders was 35 aircraft with 8 airlines.

The disasters at Elba and Naples stopped everything. Production of the Series 2 had been in full swing, and there were no fewer than 25 aircraft in various stages of assembly. All commercial orders were cancelled.

After the inquiry, an assessment was made about how to salvage the Series 2. De Havilland, with support from the RAE, prepared a package of modifications to upgrade the aircraft to proper strength and deal with a number of peripheral concerns. Changes included re-skinning the fuselage, extensive structural reinforcement, oval cabin windows, and directing the engine exhaust away from the fuselage. Assembled aircraft were deemed too expensive to modify completely, and were re-certified for unpressurised use only. In total, 15 out of 25 Comet 2s were saved, 8 of which were fully modified.

All serviceable Comet 2s went to the Ministry of Supply, 13 being redistributed to the RAF, who suddenly and unexpectedly found themselves with the largest fleet of high-speed military transports in the world. As a result, they were used for all kinds of tasks at home, or leased and lent abroad. In America, two Comets assisted as high-speed flying laboratories during calibration of air-to-air guided missiles. Another, flown by de Havilland test pilot, Ron Clear, and full of state-of-the-art monitoring equipment, recorded the ascent of the first Gemini missions for NASA.

The last Comet 2 was retired from service on 10 January 1975.